An example of such a device is a so-called ACC system (adaptive cruise control), which makes it possible, among other things, to adapt the speed of the vehicle to the speed of a preceding vehicle that has been located with the aid of a radar system, so that the preceding vehicle is followed at a suitable safe distance. To do this, the ACC system intervenes in the drive system and, if necessary, also the braking system of the vehicle. Thus, in this case there are two actuators, namely, the drive system and the braking system, and the reference variables refer to the acceleration by way of the drive system and/or the braking slowdown. The reference variables may each be also described by an executive function over a specified time period.
ACC systems currently being used are generally designed for travel at higher speeds, for instance, on express highways. In this context, there will generally be only slight accelerations and slowdowns, and the reference variables have only low dynamics, i.e. small rates of change over time, which the actuators are able to follow with negligible time delay.
However, if such longitudinal guidance systems are also to be used in situations that are characterized by greater dynamics, for example, in stop-and-go traffic or in urban traffic, then the dynamic behavior of the actuators can often be no longer ignored.